In Bahrain, Iran and Syria, tough rulers are using social media to entrap activists and crowd source the identity of people who attend protests. After Anders Breivik’s massacre in Norway, flash mobs in Philadelphia and the violent rioters in England and Vancouver, some people have been tempted to blame the Internet, specifically social media, for the violence. It may be appealing political rhetoric but is certainly wrong — and dangerous to act on.

Breivik left a trail of hatred in chat rooms, and “liked” neo-Nazi groups on Facebook. He may have been radicalized by reading hate writings online, and he may even feel vindicated by the online rhetoric of radicals in other countries. Urban youth from London to Vancouver and Philadelphia have used their Blackberries and Twitter accounts to brag about violent exploits, prompting the British Prime Minister David Cameron to say that “everyone watching these horrific actions will be struck by how they were organized via social media.”

Yet it was only six months ago that young civic leaders in North Africa and the Middle East used social media to activate the most significant popular movement for democracy those regions have seen in decades. If the upside of social media is the inspiring Arab Spring, is the downside unpredictable criminal destruction and political repression?

Social media can draw in lots of people quickly through network effects. Perhaps too quickly for most hierarchical security agencies. Research on the properties of networks demonstrates that they can be powerful tools for encouraging anti-social opinion and behavior. Social scientists at Syracuse University recently theorized that it would only take 10 percent of a population distributed by social networks to the right places to radically alter public opinion and large-scale behaviors. But what happened in London and Oslo shouldn’t be labeled acts of civil disobedience. Breivik was a deranged loner, and London’s rioters were motivated by material gain, not political ideology.

Indeed, there is evidence that social media networks have two structurally good features.

First, like other broadcast media, social media networks are tools for socialization. With social media, radical political actors do find audiences and crackpot theories do find believers, but they both tend to get marginalized in minor sub-networks. Anti social behavior typically gets blocked at “choke points”, mandatory points of passage for new ideas, and get contained in small sub-networks by people who don’t think criminal or terrorist ideas should spread. Research shows that in young democracies around the world, radical political parties have either softened their message through social media to reach young tech-savvy voters or have been relegated to the periphery. What we need is more people on social media, not less, to drown hate with reason.

Second, in democracies where authorities track illegal behavior, Facebook and Twitter should make it easier for security agencies to map networks of criminals foolish enough to brag about their exploits online. After Vancouver’s riots, the police used Twitter records and Facebook images to track down looters.

But there is a more fundamental question before modern democracies. Since we know that social media creates new opportunities for political conversation and civic action, should we really be shutting down social media in fear of what might occur? It happened last week in San Francisco: the Bay Area Rapid Transit authority disabled cell phone networks on its trains in anticipation of a protest. In the UK, two young men were handed a 4 year prison sentence for inciting riots over Facebook. Is this a proportionate response from the justice system?

Without evidence that public safety is at risk, preventing social protest is a dubious move. Political leaders may be struck by the speed at which a crisis can spin out of their control, but controlling social media to circumvent collective action is a bad idea. Ultimately, social media works because messages pass over networks of trust and reciprocity, resonating with friends and family. The world needs more trust and reciprocity, not less. Similarly, the world needs more social media, not less.